Wearable transcutaneous electrical acupoint stimulation bracelet for prevention of postoperative nausea and vomiting in patients undergoing hysteroscopic surgery: a randomised controlled trial

Editor—Postoperative nausea and vomiting (PONV) is the most common complication of surgery and anaesthesia besides pain. The overall incidence of PONV after general anaesthesia is 30–60%, and can be as high as 80% in high-risk populations.1Apfel C.C. Heidrich F.M. Jukar-Rao S. et al.Evidence-based analysis of risk factors for postoperative nausea and vomiting.Br J Anaesth. 2012; 109: 742-753Abstract Full Text Full Text PDF PubMed Scopus (446) Google Scholar Drug therapy is currently the primary treatment for PONV, but concerns about cost and side-effects have led to an increasing interest in developing non-pharmacological approaches.2Gan T.J. Belani K.G. Bergese S. et al.Fourth consensus guidelines for the management of postoperative nausea and vomiting.Anesth Analg. 2020; 131: 411-448Crossref PubMed Scopus (351) Google Scholar The pericardium 6 acupuncture point (PC6) stimulation is one of the most well-studied approaches and has proved to be effective.3Frey U.H. Scharmann P. Löhlein C. et al.P6 acustimulation effectively decreases postoperative nausea and vomiting in high-risk patients.Br J Anaesth. 2009; 102: 620-625Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar The archetypal PC6 stimulation includes acupuncture and acupoint injection, both of which are invasive procedures that carry a risk of bleeding and infection.4Takahashi T. Acupuncture for functional gastrointestinal disorders.J Gastroenterol. 2006; 41: 408-417Crossref PubMed Scopus (180) Google Scholar Recent studies have reported the effectiveness of transcutaneous electrical acupoint stimulation (TEAS).5Lee A. Chan S.K. Fan L.T. Stimulation of the wrist acupuncture point PC6 for preventing postoperative nausea and vomiting.Cochrane Database Syst Rev. 2015; 2015: CD003281Google Scholar The EmeTerm bracelet (WAT Medical Enterprise, Ltd., Vancouver, BC, Canada) is a new wearable TEAS device that does not require conductive gel and is popular in preventing motion sickness and morning sickness, but its role in PONV has not been reported. Hysteroscopic surgery is usually performed as an outpatient procedure. Patients are often exposed to more than one risk factor for PONV,6Dabu-Bondoc S. Vadivelu N. Shimono C. et al.Intravenous dextrose administration reduces postoperative antiemetic rescue treatment requirements and postanesthesia care unit length of stay.Anesth Analg. 2013; 117: 591-596Crossref PubMed Scopus (26) Google Scholar thus it is crucial to consider the possible extended hospitalisation and increased costs associated with PONV. Therefore, we aim to test the efficacy of TEAS using the EmeTerm bracelet in patients undergoing hysteroscopy. Ethical approval (the Ethics Committee of the Second Affiliated Hospital of Naval Medical University, CZEC2020-01), registration (Chinese Clinical Trial Registry, March 31, 2020, ChiCTR2000031421), and written informed consent were obtained. A total of 295 adult female patients (≥18 yr old), American Society of Anesthesiologists physical status 1–2, who were scheduled for hysteroscopic surgery, were enrolled from April 2020 to October 2021. Exclusion criteria were: pregnant or lactating, severe liver or renal dysfunction, or use of antiemetics preoperatively. Participants were randomly allocated to the TEAS group or the control group in a 1:1 ratio using sealed envelopes. Subjects in the TEAS group wore the bracelet with the electrodes placed at the PC6 acupoint (on the volar side of the forearm, 3–5 cm proximal to the wrist stripes, between the palmaris longus tendon and the radial flexor carpi tendon). The investigator switched on the bracelet and chose the third level, where patients could feel slight numbness on the radial side of the palm, whereas finger movement was unaffected. Thereafter, a cotton wristband was worn to conceal the bracelet, keeping it blind to the observer. The bracelet was worn for 24 h postoperatively. Patients in the control group received the same intervention except that the bracelet was not switched on. General anaesthesia was induced and maintained by an established protocol (Supplementary material). Subjects were followed up at 1, 6, and 24 h postoperatively by an observer who was blinded to the allocation. The primary outcome was incidence of PONV at 0–24 h and was by intention-to-treat, where worst-case imputation was used for missing data. A per-protocol analysis was performed to enhance the results. Secondary outcomes included PONV incidence during different follow-up periods and the percentage of subjects who achieved a complete response, defined as no vomiting or use of rescue medication. Sample size was calculated based on the primary outcome. The incidence of PONV was estimated to be 60% in the control group according to our previous research, and the intervention was expected to produce a 30% improvement, so incidence was projected to be 42% in the TEAS group. Therefore, 236 subjects were required to achieve 80% power with a type-I error of 0.05. Allowing for a 10% dropout rate, 260 participants were recruited. Categorical variables were analysed using Fisher's exact test. A two-sided P-value <0.05 was considered statistically significant. We recruited 122 subjects in the TEAS group and 124 in the control group who completed the study (CONSORT flow diagram and patient characteristics in Supplementary material). The intention-to-treat analysis indicated that the incidence of PONV in the TEAS group was lower than that in the control group (38.5% vs 52.3%, P=0.034) within the first 24 h after surgery. The risk of PONV was reduced by 26% (95% confidence interval [CI] 4–44%). The absolute difference was 0.14 (95% CI 0.02–0.26), which means that one in seven patients would benefit from the intervention. The results of the per-protocol analysis agreed with the intention-to-treat analysis (34.4% vs 50.0%, P=0.015). The incidence of nausea in the TEAS group was not significantly different from that in the control group (15.6% vs 13.7%, P=0.721), whereas the incidence of vomiting was lower (18.9% vs 36.3%, P=0.003) (Table 1, details in Supplementary material).Table 1The incidence of postoperative nausea and vomiting and secondary outcomes in follow-up. Data are presented as n (%).TEAS groupControl groupPIntention-to-treat analysisn=130n=1300–24 h PONV50 (38.5)68 (52.3)0.034Per-protocol analysisn=122n=1240–24 hPONV42 (34.4)62 (50.0)0.015Nausea19 (15.6)17 (13.7)0.721Vomiting23 (18.9)45 (36.3)0.0030–1 hPONV13 (10.7)13 (10.5)0.965Nausea5 (4.1)6 (4.8)0.779Vomiting8 (6.5)7 (5.7)0.765Antiemetic1 (0.8)0 (0)0.496Complete response113 (92.6)117 (94.4)0.6151–6 hPONV36 (29.5)53 (42.7)0.031Nausea18 (14.8)18 (14.5)0.958Vomiting18 (14.8)35 (28.2)0.010Antiemetic4 (3.28)3 (2.42)0.983Complete response100 (82.0)86 (69.4)0.0266–24 hPONV21 (17.2)27 (21.8)0.367Nausea11 (9.0)10 (8.1)0.789Vomiting10 (8.2)17 (13.7)0.167Antiemetic0 (0)1 (0.8)1.000Complete response112 (91.8)106 (85.5)0.160PONV, postoperative nausea and vomiting; TEAS, transcutaneous electrical acupoint stimulation.Categorical variables were analysed using Fisher's exact test. Open table in a new tab PONV, postoperative nausea and vomiting; TEAS, transcutaneous electrical acupoint stimulation. Categorical variables were analysed using Fisher's exact test. There was no significant difference between groups during 0–1 h and 6–24 h. However, the incidences of PONV and vomiting, and complete response rate, were significantly lower in the TEAS group than those in the control group during 1–6 h and 0–24 h, whereas the incidence of nausea was not significantly different. Therefore, we concluded that TEAS was effective in preventing PONV, especially vomiting (i.e. TEAS reduced the severity of PONV). This finding is consistent with previous studies.7Yang X.Y. Xiao J. Chen Y.H. et al.Dexamethasone alone vs in combination with transcutaneous electrical acupoint stimulation or tropisetron for prevention of postoperative nausea and vomiting in gynaecological patients undergoing laparoscopic surgery.Br J Anaesth. 2015; 115: 883-889Abstract Full Text Full Text PDF PubMed Scopus (46) Google Scholar,8Chen J. Tu Q. Miao S. et al.Transcutaneous electrical acupoint stimulation for preventing postoperative nausea and vomiting after general anesthesia: a meta-analysis of randomized controlled trials.Int J Surg. 2020; 73: 57-64Crossref PubMed Scopus (35) Google Scholar The incidence of PONV in our study was lower than that in other gynaecological surgeries.9Massoth C. Schwellenbach J. Saadat-Gilani K. et al.Impact of opioid-free anaesthesia on postoperative nausea, vomiting and pain after gynaecological laparoscopy - a randomised controlled trial.J Clin Anesth. 2021; 75: 110437Crossref PubMed Scopus (29) Google Scholar This could be explained partly by the shorter exposure to surgery and anaesthesia, and the lower dosage of opioids.10Apfel C.C. Kranke P. Eberhart L.H. Comparison of surgical site and patient's history with a simplified risk score for the prediction of postoperative nausea and vomiting.Anaesthesia. 2004; 59: 1078-1082Crossref PubMed Scopus (97) Google Scholar A placebo effect from wearing the bracelet may have some impact. Therefore, the effectiveness of TEAS was perhaps not fully reflected. Few adverse effects were noted. Two patients (0.77%, 2/260) reported suspected allergy manifested as local redness and slight itching, and the symptoms disappeared 12–24 h after the removal of the bracelet without any special treatment. Three patients (1.2%, 3/260) reported unbearable numbness in their hand. The symptoms disappeared immediately after the bracelet was removed, and no discomfort was reported the following day. In conclusion, a new wearable transcutaneous electrical acupoint stimulation bracelet is effective in preventing postoperative nausea and vomiting in patients undergoing hysteroscopic surgery. The authors declare that they have no conflicts of interest. National Natural Science Foundation of China (81873945); Military Medical Talent Plan of Naval Medical University (2019-YH-11); Innovating Projects for the Army (2020CZWJFW09); Medical Innovation Research Project of Shanghai Science and Technology Commission (21Y11906400); Innovative Clinical Research Project of the Second Affiliated Hospital of Naval Medical University (2020YLCYJ-Y18); Advanced and Appropriate Technology Promotion Project of Shanghai Municipal Health Commission (2019SY019).